Aluminum (Al)-ion batteries have emerged as a potential alternative to conventional ion batteries that rely on less abundant and costly materials like lithium. Nonetheless, given the nascent stage of advancement in Al-ion batteries (AIBs), attaining electrode materials that can leverage both intercalation capacity and structural stability remains challenging. Herein, we demonstrate a C3N4-derived layered N,S heteroatom-doped carbon, obtained at different pyrolysis temperatures, as a cathode material for AIBs, encompassing the diffusion-controlled intercalation and surface-induced capacity with ultrahigh reversibility. The developed layered N,S-doped corbon (N,S-C) cathode, synthesized at 900 degrees C, delivers a specific capacity of 330 mAh g(-1) with a relatively high coulombic efficiency of similar to 85% after 500 cycles under a current density of 0.5 A g(-1). Owing to its reinforced adsorption capability and enlarged interlayer spacing by doping N and S heteroatoms, the N,S-C900 cathode demonstrates outstanding energy storage capacity with excellent rate performance (61 mAh g(-1) at 20 A g(-1)) and ultrahigh reversibility (90 mAh g(-1) at 5 A g(-1) after 10 000 cycles).

Recently, a 2D metal boride - boridene - has been experimentally realized in the form of single-layer molybdenum boride sheets with ordered metal vacancies, through selective etching of the nanolaminated 3D parent borides (Mo_2/3Y_1/3)₂AlB₂ and (Mo_2/3Sc_1/3)₂AlB₂. The chemical formula of the boridene was suggested to be Mo_4/3B_2-xT_z, where T_z denotes surface terminations. Here, the termination composition and material properties of Mo_4/3B_2-xT_z from both theoretical and experimental perspectives are investigated. Termination sites are considered theoretically for termination species T = O, OH, and F, and the energetically favored termination configuration is identified at z = 2 for both single species terminations and binary termination mixes of different stoichiometries in ordered and disordered configurations. Mo_4/3B_2-xT_z is shown to be dynamically stable for multiple termination stoichiometries, displaying semiconducting, semimetallic, or metallic behavior depending on how different terminations are combined. The approximate chemical formula of a freestanding film of boridene is attained as Mo_1.33B_1.9O_0.3(OH)_1.5F_0.7 from X-ray photoelectron spectroscopy (XPS) analysis which, within error margins, is consistent with the theoretical results. Finally, metallic and additive-free Mo_4/3B_2-xT_z shows high catalytic performance for the hydrogen evolution reaction, with an onset potential of 0.15 V versus the reversible hydrogen electrode.

Zircaloy coating is one of the crucial technical ways to improve the accident tolerance of nuclear fuel cladding, which enables the zirconium-water reaction problems to be solved. Zr2Al3C4 coating is one type of candidate solutions to improve the high-temperature oxidation resistance of zirconium claddings. However, little study has been performed on the synthesis of Zr2Al3C4 coatings on zirconium alloy substrates due to the inter-diffusion, as well as the difference of the thermal expansion coefficients between the Zr2Al3C4 coating and the substrates. In this study, Zr2Al3C4 coatings were prepared through room-temperature magnetron sputtering and post annealing on zirconium alloy (ZIRLO) substrates with magnetron-sputtered Al/Mo-C interlayers. The effects of Al/Mo-C interlayers on phases and microstructures of Zr-Al-C coatings after annealing were studied by different methods. It is found that the coatings without interlayer are broken and no Zr2Al3C4 phase is formed due to significant interdiffusion between the Zr-Al-C coating and the substrate during annealing at 800 degrees C for 3 h. The Al/Mo-C interlayers prevented elemental diffusion between Zr-Al-C coatings and substrates during the post-annealing process. The Al/Mo-C interlayers act as diffusion barriers and greatly reduce the stoichiometric deviations from Zr2Al3C4 phase, which facilitates the formation of the Zr2Al3C4 phase in the final coating. Moreover, this diffusion-barrier layers contribute to eliminating cracks induced by the difference of the thermal expansion coefficients between the Zr2Al3C4 coatings and substrates. At the same time, the adhesions between Zr-Al-C coatings with Al/Mo-C interlayers and substrates were improved after annealing, with their strength exceeding 30 N.

MXenes are a rapidly growing family of 2D materials that exhibit a highly versatile structure and composition, allowing for significant tuning of the materials properties. These properties are, however, ultimately limited by the surface terminations, which are typically a mixture of species, including F and O that are inherent to the MXene processing. Other and robust terminations are lacking. Here, we apply high-resolution scanning transmission electron microscopy (STEM), corresponding image simulations and first-principles calculations to investigate the surface terminations on MXenes synthesized from MAX phases through Lewis acidic melts. The results show that atomic Cl terminates the synthesized MXenes, with mere residual presence of other termination species. Furthermore, in situ STEM-electron energy loss spectroscopy (EELS) heating experiments show that the Cl terminations are stable up to 750 degrees C. Thus, we present an attractive new termination that widely expands the MXenes functionalization space and enables new applications.